Grinding apparatus of the abrasive belt type



Aug. 16, 1949. J, ELMES 2,479,535

GRINDING APPARATUS OF THE ABRASIVE BELT TYPE Filed July 24, 1947 l INVENTOR.

John A. Elmes.

Patented Aug. 16, 1949 GRINDING APPARATUS OF THE ABRASIVE BELT TYPE

John A. Elmes, Beaver Falls, Pa., assignor, by mesne assignments. to Ryman Engineering Company, Ellwood City, Pa., a corporation of Pennsylvania Application July 24, 1947, Serial No. 763,309

3 Claims.

My invention relates to that type of grindin apparatus wherein an abrasive belt is employed as the surfacing element for work pieces that are to be ground or polished.

The invention is particularly useful in connection with abrasive belts employed in connection with a pulley or drum that is resilient and yieldable to the pressure of work pieces applied against the belt where it passes around the pulley or roll. In devices of this character, there is dimculty in maintaining proper and uniform belt tension, owing to the yieldability of the roll at which the work is applied against the belt, and to the varying degrees of pressure with which the workman necessarily applies to the work pieces. Variations in belt tension therefore constantly occur, with the result that not only is there danger of the belt jumping off of its pulley, but there are such variations in belt tension during a grinding operation that the, belt may operate in a somewhat jerky manner making what are, in effect, chatter marks on the work.

My invention has for its object the provision of an improved means for automatically maintaining a belt under a constant desired tension during the variable conditions under which the grinding apparatus is operated, as above mentioned, particularly where the abrasive belt is employed in conjunction with a resilient roll or drum.

In the accompanying drawing, Figure l is a side elevational view of a grinding machine embodying my invention, and Fig. 2 is a view partly in elevation and partly in section, looking in the direction of the arrow II at Fig. 1.

The apparatus comprises a front stand 3 and a back stand 4 which may be of any suitable or conventional form.. A pulley or roll 5 that serves, in effect, as a. back-up pulley for an abrasive belt 6, when work pieces are applied to the belt while it is passing around the roll, is mounted on a shaft 1 having a driving pulley 8 that is driven by a motor 9.

The abrasive belt may be of any suitable conventional material, as for example jeans cloth which is faced with emery, aluminum oxide granules or the like.

The roll 5 may be of any suitable resilient construction but is here shown as formed of felt discs ll thatare assembled in laminated arrangement to form a roll of the desired width. The discs are secured to a hub l2 that is, in turn, secured to the shaft 1. The roll is highly yieldable and may be compressed to a depth of an inch or more by work applied against theiace of 2 a belt, depending somewhat upon the diameter of the roll.

The soft roll 5, in conjunction with the sanding belt, renders the device especially suitable for grinding articles of uneven contours such as openend wrenches which have both concave and convex surfaces'to be ground, since the roll is compressible to a degree that will cause the belt to flex to an extent sufficient to enable it to reach depressions in a work piece.

A guide or idler pulley 13 of anyconventional form is iournaled on a bracket it that is mounted on a shaft 15 that is supported at each end by a post l6 forming part of the back stand 4. The bracket 14 has a crank arm I! extending therefrom, so that when said arm is rocked about the axis of the shaft IS, the pulley l3 will be moved to change the tension of the belt 6.

The pulley i3 is automatically rocked about the axis of the shaft l5 to maintain the abrasive belt 6 under a desired tension. To this end, I provicle a cylinder l8 that contains a piston IS. A piston rod 20 connects the piston with the arm ll, so that if the piston is moved up and down, the pulley l3 will be rocked.

Fluid pressure is supplied to the cylinder from a suitable source, through a pipe 21, pressure regulator 22, a 4-way valve 23 and pipes 24 and 25 to the upper and lower ends of the cylinder.

The pressure regulator is adjustable in order to provide a desired pressure of air in the cylinder, as is common with fluid-pressure systems of this character. be positioned so as to admit air through the pipe 25 to the underside of the piston l9, thereby maintaining the belt 6 under a desired tension, such tension being indirectly determined y reference to a pressure gauge 26 in the line between the pressure regulator 22 and the valve 23. Exhaust at this time can take place from the upper side of the piston, through the pipe 24. When it is desired to replace a belt, the valve 23 will be turned to exhaust pressure from the lower end of the cylinder and also admit pressure to the upper end of the cylinder.

A guard plate 28 is positioned above the upper run of the belt and is carried by the roll stands.

The belt may be driven at various speeds, as for example from 800 feet per minute to 3000 feet per minute, and air pressures of 15 to 20 lbs. will usually be suitable with the smaller machines where the work is pressed against the belt and the pulley 5 by hand.

It will be seen that because a constant supply of air at predetermined pressure is maintained The 4-way valve will normally I 'tions in the frictional 'force of the belt upon the work piece. There will thus be not only uniformity of abrasive action, but the belt will be held against tightening and loosening eilEects which would cause it to slip or jump off the pulleys. This is in contrast to spring-pressure devices wherein the springs do not yield with uniformity throughout their entire range of yielding movement, and therefore the abrasive belt would not be maintained under so accurately uniformed tension. Furthermore, a spring would be more subject to vibrations under operating conditions than is the case where a pneumatic tensioning means of continuing uniformity are employed as here.

I claim as my invention:

1. A grinding and polishing machine comprising an abrasive belt, a driving pulley and a guide pulley for the belt, the drive pulley being of resiliant construction, and a pneumatic pressure device for urging the guide pulley in a direction away from the driving pulley, to thereby yieldably maintain the belt under tension.

2. A grinding and polishing machine comprising a pulley of resilient construction, that is yieldable under the application of working pressures thereto, a second pulley, an abrasive belt extending around the pulleys, and a pneumatic pressure device for urging one of the pulleys in 4 a direction to maintain the abrasive belt under tension.

3. A grinding and polishing machine comprising a front stand having a pulley of resilient construction mounted thereon, a back stand having a bracket pivoted thereon on an axis parallel to the pulley axis, a pulley carried by the bracket, a crank arm extending from the bracket, 9. piston rod connected to the outer end of the arm, a piston for the said rod, a cylinder for the piston, an abrasive belt extending around the pulleys, and means for admitting pneumatic pressure into the cylinder to effect rocking of the bracket in girltections to control the tension of the abrasive JOHN A. ELMES.

REFERENCES (IITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

